This invention relates to an improved belt conveyor for signatures, loose sheets, gathered or pamphletized sheets, and the like, having a device for picking them up. Such conveyors are utilized in particular in bookbindery.
Conveyors of this same general type are known per se. They usually comprise a supporting frame and a substantially horizontal feeder belt run, as well as a substantially sloping elevator belt run forming an obtuse angle with the run of the conveyor belts feeding the signatures or the like. Such feeder belts are operated at a substantially lower speed than said elevator belts.
The practical problem is encountered with known conveyors that, owing to the low speed of the feeder belts, a stack of signatures, loose sheets, gathered sheets or the like (hereinafter referred to as "signatures", for simplicity) is subjected to a forward pushing force which is only applied to that side of the signatures which contacts the feeder belts, so that in the proximity of the transition or transfer area from the horizontal feeder belts to the elevator belts, a frictional engagement action is exerted on the bottom portion of the signatures tending to open them fan-like at the top and cause them to slope or lean towards the feeder belts, especially with small size and thick signatures.
The problem is further enhanced by the use of comparatively rigid signatures.
Thus, an operator's presence is required on a continued basis to prevent the signatures from being tilted rearwardly.
Moreover, conventional conveyors have the disadvantage that the signatures are picked up upon completion of the upward transport of the foremost signature, which is due to the substantial lack of impact between the signature following the foremost signature which is being picked up by the elevator belts.
This phenomenon is obviously specially evident in the case of particularly rigid signatures, or signatures of appreciable thickness. This phenomenon reflects, moreover, in a longer time for the formation of the stacks downstream of the elevator belts.